Tilda Swinton is sleeping in a glass box in the Museum of Modern Art (MoMA) in New York City.

The Moonrise Kingdom actress is the star of a new performance art installation called The Maybe, that involves her spending her days snoozing in the transparent box, simply equipped with a mattress, bed sheets and a jug of water, in front of visitors.

The 52-year-old Oscar winner's surprising showcase will be taking place on random days throughout the rest of this month.

According to Gothamist.com, even staff at the museum doesn't know when the Scottish star will appear.

The quirky actress conceived the installation nearly two decades ago and performed it for the first time in 1995 at London's Serpentine Gallery, and followed up with a second showing in Rome a year later.

MoMA has only offered a brief explanation for the art show, choosing instead to let it speak for itself: "An integral part of The Maybe's incarnation at MoMA in 2013 is that there is no published schedule for its appearance, no artist's statement released, no museum statement beyond this brief context, no public profile or image issued.

"Those who find it chance upon it for themselves, live and in real - shared - time: now we see it, now we don't."